The present invention relates generally to digital imaging systems and, more particularly, to a calibration and setup procedure for determining a separation distance between a radiation source and a digital detector in a digital imaging system.
The installation and setup procedures for digital imaging systems, such as radiographic diagnostic imaging systems, can be complex and time-consuming. For example, to comply with customer image quality and consistency requirements and various regulatory and safety standards for diagnostic imaging systems, such procedures generally require the determination of a variety of factors, including the accurate positioning of the x-ray source with respect to the x-ray detector. For instance, the determination and establishment of fixed setpoints (or detent positions) for setting the separation distance between the x-ray source and x-ray detector and calibrating the system such that an accurate readout of the separation distance can be obtained often are required procedures. The determination and establishment of this separation distance, referred to as the source-to-image distance (SID), assists in appropriately controlling the size of the x-ray field during diagnostic use of the imaging system. Further, many regulatory requirements specify that the SID must be clearly displayed to the operator or user of the system with a certain level of accuracy.
Generally, known installation and calibration procedures for establishing fixed SID setpoints and corresponding SID readouts require the presence of a field engineer who, through a trial and error process, calibrates the radiographic imaging system and installs fixed, preset detent positions that lock the x-ray source into various repeatable separation distances from the detector. For example, the field engineer may install an electromechanical switch, or other device, in the ceiling or the superstructure of the x-ray source that indicates to the user in a tactile or otherwise perceptible manner that the x-ray source is at one of the preset SID positions. Many radiographic imaging systems include industry-standard SID setpoints at separation distances of, for example, 40 inches, 60 inches, and 72 inches.
The installation and calibration procedure, however, becomes even more complex if the detector also is non-stationary. In such event, the field engineer must repeat the setup and calibration procedure at multiple detector positions and install several setpoint or detent devices at the corresponding multiple determined SID positions.
Once the preset SID positions are determined and marked with a detent device, the SID positions are fixed. Thus, a user of the imaging system is not afforded flexibility in the event that the user may desire an SID position that is non-standard. Accordingly, even though either the x-ray source or the x-ray detector could be moved to a variety of different positions such that patients of various sizes could be accommodated or various anatomical parts could be more easily imaged, the actual positions in which the x-ray source could be located with respect to the x-ray detector are restricted to only those few positions which have corresponding fixed detent setpoints.
Preset fixed setpoints can also result in decreased system reliability because the physical switches or detent devices increase the number of components which can potentially fail during system usage.
Thus, it would be desirable to provide a system and method for installing and calibrating a digital radiographic imaging system that would avoid time-consuming iterative procedures for determining fixed SID positions and for providing a calibrated readout and display of the actual SID. It would be further desirable if such a system and method would result in the elimination of, or reduced reliance on, fixed setpoints and physical fixed setpoint devices, thus affording greater flexibility and increasing the reliability of the system.
The present invention addresses one or more of the shortcomings noted above.
For example, a method for determining a separation distance between a radiation source and a digital detector comprises the steps of detecting a first impact region on the detector of a first radiation beam generated by the source while at a first source position, determining a first size of the first impact region, and varying a size of a collimator opening through which radiation beams generated by the source are directed. A second impact region on the detector of a second radiation beam is then detected, the second radiation beam being generated by the source while at the first source position and being directed through the varied size of the collimator opening such that the second impact region has a second size different than the first size. The second size is determined, and the separation distance is determined based on the variation of the size of the collimator opening and the determined first and second sizes of the first and second impact regions.
A digital imaging system is also provided which includes a digital detector configured to detect radiation beams, a radiation source to generate radiation beams, and a processing module. The source includes a collimator having a collimator opening through which the radiation beams are directed. The radiation source is configured to generate a first radiation beam detectable by the detector while the source is at a first source position and while the collimator opening is at a first size. The radiation source is also configured to generate a second radiation beam detectable by the detector while the source is at the first source position and while the collimator opening is at a second size. The processing module is configured to determine the first size of the first impact region of the first radiation beam detected by the detector and the second size of the second impact region of the second radiation beam detected by the detector. The processing module is further configured to determine a separation distance corresponding to the first source position based on the first and second sizes of the collimator opening and the first and second sizes of the impact regions.